Various methods and composites for reinforcing asphaltic roads and overlays have been proposed. Some describe fiberglass grids impregnated with resins. To repair an old pavement, an asphaltic tack coat is generally applied with fiberglass grids according to construction regulations. The tack coat is applied as a liquid (for example, as an emulsion or hot asphalt cement binder by spraying), and thereafter changes from a liquid to a solid. The tack coat is applied on top of the installed grid with an adhesive coating on the back of the grid, used as an aid in bonding a new asphalt payment to the existing pavement surface. In order to install fiberglass grids without adhesive coating on the back of the grid, the tack coat is firstly applied to an existing pavement. Before the tack coat is fully cured, the grid is laid on the tack coat. As the tack coat cures further, it holds the grid in place on the underlying pavement. The tack coat partially dissolves and merges with the impregnating resin in the grid, when hot asphalt concrete is overlaid on top of the grid. Tack coats have several highly desirable features for use with such reinforcements. In particular, they are compatible with the asphaltic concrete or cement to be used as the overlay, and their fluid nature makes them flow into, and smooth out, rough paving surfaces.
On the other hand, tack coats present several difficulties. The properties of tack coats are very sensitive to ambient conditions, particularly temperature, and humidity. These conditions may affect cure temperature of emulsion tack coats, and in severe conditions, they can prevent cure. In less severe circumstances, the overlay paving equipment must wait until the tack coat has cured, causing needless delays. For example, tack coats are normally emulsions of asphalt in water, often stabilized by a surfactant. To manifest their potential, the emulsion must be broken and water removed prior to lay down a film of asphalt. The water removal process is, essentially, evaporation, which is controlled by time, temperature, and humidity of the environment. Frequently, the environmental conditions are unfavorable, resulting in inefficient tacking or unacceptable delay.
U.S. Pat. No. 8,038,364 describes a tack film that can be used in conjunction with a reinforcing grid to repair asphaltic pavement. The reinforcing grid and tack film is laid over a base layer and a heated asphalt material is laid on top of the film. The tack film may include a polyethylene core with a resinous coating of, for example, an ethylene vinyl acetate. The tack film is softened and melted into a single body by the heat of the asphalt material. However, the film does not melt adequately unless the asphalt is applied at a temperature of greater than 285° F. While conventional hot asphalt mix is required to a temperature of 250° F. and above, the tack film fails to melt and adhesively bond to asphalt at temperatures less than 285° F.
Accordingly, there remains a desire to improve the adhesive bond between pavement courses and in particular, at low temperature paving conditions.